Halos show the path to perfection: peripheral iodo-substituents improve the e ﬃ ciencies of bis(diimine) copper( I ) dyes in DSCs †

The homoleptic copper( I ) complexes [CuL 2 ][PF 6 ] (L ¼ 4,4 0 -bis(4-halophenyl)-6,6 0 -dimethyl-2,2 0 -bipyridine with halogen ¼ F ( 2 ) and Cl ( 3 )) have been prepared and characterized, and their absorption spectroscopic and electrochemical properties compared to that with L ¼ 4,4 0 -bis(4-bromophenyl)-6,6 0 -dimethyl-2,2 0 - bipyridine ( 4 ). The synthesis of [CuL 2 ][PF 6 ] (L ¼ 4,4 0 -bis(4-iodophenyl)-6,6 0 -dimethyl-2,2 0 -bipyridine, 5 ) resulted in a mixture of [Cu( 5 ) 2 ][PF 6 ] and [Cu( 5 )(MeCN) 2 ][PF 6 ]; variable temperature 1 H NMR spectroscopy con ﬁ rmed that the complexes are in equilibrium in CD 3 CN solution. The structure of [Cu( 5 )(MeCN) 2 ][PF 6 ] was determined by single crystal X-ray crystallography, and con ﬁ rms a distorted tetrahedral geometry for the copper( I ) centre. The heteroleptic dyes [Cu( 1 )( 2 )] + , [Cu( 1 )( 3 )] + , [Cu( 1 )( 4 )] + and [Cu( 1 )( 5 )] + ( 1 ¼ ((6,6 0 -dimethyl-[2,2 0 -bipyridine]-4,4 0 -diyl)bis(4,1-phenylene))bis(phosphonic acid)) have been assembled by ligand exchange between [CuL 2 ] + and TiO 2 functionalized with the anchoring ligand 1 , and the performances of the dyes in fully masked dye-sensitized solar cells (DSCs) have been measured and compared. On the day of DSC fabrication, the trend for the global e ﬃ ciencies, h , depends on the halo-substituent in the order I > F z Br > Cl. Ripening of the DSCs occurs and after 7 days, the dependence of h on the halo-atom is in the order I > Cl z F z Br; the highest h is 3.16% for [Cu( 1 )( 5 )] + compared to 7.63% for N719. Compared to the other halo-functionalized dyes, [Cu( 1 )( 5 )] + shows an extended spectral response to longer wavelength, with enhanced electron injection. The results of DFT calculations suggest that the better dye performance of [Cu( 1 )( 5 )] + may be associated with improved electron transfer over the halogen of the aryl substituent from the reduced electrolyte. The assembly of anchored dye [Cu( 1 )( 5 )] + by treating functionalized-TiO 2 with a 1 : 1 mixture of [Cu(MeCN) 4 ] + and 5 , yields a dye which gives a DSC performance that matches that made by ligand exchange using [Cu( 5 ) 2 ][PF 6 ] and [Cu( 5 )(MeCN) 2 ][PF 6 ].


Introduction
Pioneering studies by Sauvage and co-workers in the 1990s established the potential use of copper(I) complexes in dyesensitized solar cells (DSCs). 1 Nonetheless, ruthenium(II)-containing photosensitizers remain the mainstay of conventional Grätzel-type DSCs. 2 For sustainable future technologies, it is necessary to develop a materials chemistry in which scarce elements are replaced by more abundant ones.[5][6][7][8][9][10][11][12][13][14] While the photophysical properties of [Cu(N^N) 2 ] + (N^N ¼ diimine ligand) are similar to those of ruthenium(II) complexes, 15,16 the greater global abundance and lower cost of copper compared to ruthenium make copper-containing dyes relevant and topical.A ground-breaking photoconversion efficiency for a DSC of 4.66% has recently been reported by Odobel, Boujtita and coworkers using a heteroleptic copper(I) dye containing the sterically demanding 6,6 0 -dimesityl-2,2 0 -bipyridine-4,4 0 -dicarboxylic acid anchoring ligand and a 2,2 0 -bipyridine ancillary ligand with hole-transporting triphenylamino units; the high efficiency of the DSC was achieved in part by using the co-adsorbent chenodeoxycholic acid (cheno). 17n contrast to the HETPHEN approach used by the Odobel group, 17 we have developed a stepwise method of assembling copper(I) dyes in n-type DSCs commencing with the absorption of an anchoring ligand, L anchor , onto the n-type semiconductor surface.Subsequent reaction of the functionalized surface with a labile homoleptic complex [Cu(L ancillary ) 2 ] + in solution leads to the formation of surface-bound dye [Cu(L anchor ) (L ancillary )] + . 4solation of the heteroleptic complex is, therefore, avoided; indeed, isolation is not usually possible because of rapid equilibration between homo-and heteroleptic cations in solution to give a statistical mixture of species.In an earlier investigation, surface-bound [Cu(L anchor )(L ancillary )] + species were characterized by MALDI-TOF mass spectrometry and diffuse reectance electronic absorption spectroscopy. 18The favoured anchoring ligand is the bis(phosphonic acid) 1 (Scheme 1), with the spacer between the 2,2 0 -bipyridine and phosphonic acid anchoring domains leading to enhanced performance of the dye. 6Our dye assembly strategy is advantageous in that it permits rapid screening of different families of ancillary ligands, and has recently been implemented by the Robertson group. 9However a disadvantage is the wastage of one equivalent of ancillary ligand, and this is particularly unsatisfactory when synthesis of the latter is a labour intensive multistep procedure.
Recently, we demonstrated that masked DSCs containing the dye [Cu(1)(L ancillary )] + in which L ancillary is 4,4 0 -bis(4-bromophenyl)-6,6 0 -dimethyl-2,2 0 -bipyridine reached power conversion efficiencies of 2.31%, compared to 8.30% for standard dye N719. 6ince ancillary ligands in n-type dyes typically incorporate electron-donating domains, we were somewhat surprised that dyes containing peripheral bromophenyl substituents (selected to provide an active site for further derivatization) performed relatively well. 6We were, therefore, prompted to study the effects of altering the halo-substituent and now report the remarkably high power conversion efficiencies of DSCs incorporating the series of ancillary ligands 2-5 (Scheme 1).We also illustrate that complete conversion of [Cu(MeCN) 4 ] + to [Cu(L ancillary ) 2 ] + is not an essential step prior to ligand exchange on the functionalized TiO 2 surface, and introduce a stepwise strategy for in situ assembly of the surface-anchored copper(I) dye.

Experimental
General A Bruker Avance III-500 NMR spectrometer was used to record 1 H and 13 C NMR spectra, and chemical shis were referenced to residual solvent peaks with respect to d(TMS) ¼ 0 ppm.Solution absorption spectra were recorded with a Cary 5000 spectrophotometer and FT-IR spectra of solid samples on a Perkin Elmer UATR Two spectrometer.Electrospray ionization (ESI) mass spectra were recorded on a Bruker esquire 3000 plus instrument.
Electrochemical measurements were made using a CH Instruments 900B potentiostat with glassy carbon, platinum wire and silver wire as the working, counter, and reference electrodes, respectively.Substrates were dissolved in HPLC grade CH 2 Cl 2 (ca. 10 À4 to 10 À5 mol dm À3 ) containing 0.1 mol dm À3 [ n Bu 4 N][PF 6 ] as the supporting electrolyte; all solutions were degassed with argon.Cp 2 Fe was used as internal reference.The scan rate was 0.1 V s À1 .
Ground state density functional theory (DFT) calculations were performed using Spartan 14 (v.1.1.3)at the B3LYP level with a 6-31G* basis set in vacuum.Initial energy optimization was carried out at a semi-empirical (PM3) level.
The external quantum efficiency (EQE) measurements were made using a Spe-Quest quantum efficiency instrument from Rera Systems (Netherlands) equipped with a 100 W halogen lamp (QTH) and a lambda 300 grating monochromator (Lot Oriel).The monochromatic light was modulated to 3 Hz using a chopper wheel (ThorLabs).The cell response was amplied with a large dynamic range IV converter (CVI Melles Griot) and then measured with a SR830 DSP Lock-In amplier (Stanford Research).

Crystallography
Single crystal data were collected on a Bruker APEX-II diffractometer with data reduction, solution and renement using the programs APEX 22 and CRYSTALS. 23The ORTEPtype diagram and structure analysis used Mercury v. 3.0. 24,25Cu (5)

DSC fabrication and measurements
DSCs were prepared modifying the method of Grätzel. 26,27ommercial Solaronix Test Cell Titania Electrodes were used.The electrodes were rinsed with EtOH and sintered at 450 C for 30 min, then cooled to z80 C and immersed in a 1 mM DMSO solution of the anchoring ligand 1 for 24 h.The colourless electrode was removed from the solution, washed with DMSO and EtOH and dried at z60 C (heat gun).The electrode with adsorbed 1 was immersed in a 0.1 mM CH 2 Cl 2 solution of each copper(I) complex for z68 h.For the nal set of DSCs (see text), the electrode with adsorbed anchoring ligand was immersed in a CH 2 Cl 2 solution containing equimolar (0.1 mM) amounts of [Cu(MeCN) 4 ][PF 6 ] and ancillary ligand 5 for 68 h; during this time, the electrodes turned pale red-orange.
Each reference electrode was prepared by dipping a Solaronix Test Cell Titania Electrode in a 0.3 mM EtOH solution of standard dye N719 (Solaronix) for z68 h.The electrodes were washed with the same solvent used in the dipping period and dried at z60 C (heat gun).A Solaronix Test Cell Platinum Electrode was used for the counter electrode, and it was heated for 30 min at 450 C (heating plate) to remove impurities.
The two electrodes were combined using thermoplast hotmelt sealing foil (Solaronix Test Cell Gaskets) by heating while pressing them together.The electrolyte was a mixture of LiI (0.1 mol dm À3 ), I 2 (0.05 mol dm À3 ), 1-methylbenzimidazole (0.5 mol dm À3 ) and 1-butyl-3-methylimidazolinium iodide (0.6 mol dm À3 ) in 3-methoxypropionitrile; it was introduced into the DSC by vacuum backlling.The hole on the counter electrode was sealed using hot-melt sealing foil (Solaronix Test Cell Sealings) and a cover glass (Solaronix Test Cell Caps).Measurements were made by irradiating from behind using a light source SolarSim 150 (100 mW cm À2 ¼ 1 sun).The power of the simulated light was calibrated by using a reference Si cell.

Ligand synthesis and characterization
We have previously used the strategy of Kröhnke 28 to prepare compounds 3 20 and 4 5 and now extend the series of haloderivatives to compounds 2 and 5 (Scheme 2).The yield of 2 was only moderate (52.8%), and 5 proved very difficult to purify and pure material was obtained in only 10.3% yield.The electrospray mass spectra of 2 and 5 exhibited base peaks at m/z 373.

Synthesis and characterization of copper(I) complexes
We have described the complex [Cu(4) 2 ][PF 6 ] previously, 6 and the same simple strategy was adopted to prepare analogous homoleptic complexes containing ligands 2, 3 or 5.The complex crystallizes in the monoclinic space group C2/c.Atom Cu1 is in a distorted tetrahedral environment; the bite angle of the bpy unit is 81.06 (7) , and other N-Cu-N bond angles range from 106.24(9) to 124.31(8) (caption to Fig. 4).The bpy domain deviates from planarity with the angle between the planes of the pyridine rings being 13.8 .The phenyl ring containing C12 is twisted through 15.5 with respect to the plane of the pyridine ring with N1, while the corresponding angle for the   rings containing C18 and N2 is 38.7 .The difference in twist angles is associated with the packing of the cations.Face-to-face p-stacking occurs between phenylbpy domains involving the phenyl ring containing atom C12 and this leads to innite columns of cations running parallel to the c-axis (Fig. 5a).The stacks are built up by alternating operations of a 2-fold axis followed by an inversion centre.The asymmetric unit contains two half-anions; each [PF 6 ] À is ordered, and atoms P1 and P2 are each located on a 2-fold axis.Cation/anion interactions involve extensive CH/F contacts.For the anion containing P1 (green in Fig. 5b), these contacts involve arene CH units; in addition this anion exhibits a short F/I contact (F3/I2 i ¼ 3.406(1) Å, symmetry code i ¼ 1/2 À x, À1/2 + y, 1/2 À z).In contrast, the anion containing P2 (red in Fig. 5b) sits between the p-stacked cations and interacts with methyl groups of both coordinated ligands 5 and MeCN.

Solution absorption spectra and electrochemistry
Absorption spectroscopic and electrochemical data were recorded only for [Cu(2) 2 ][PF 6 ] and [Cu(3) 2 ][PF 6 ] since the homoleptic complex with ligand 5 could not be obtained free of [Cu(5)(MeCN) 2 ][PF 6 ].The absorption spectra are shown in Fig. 6 and are compared with that of [Cu(4) 2 ][PF 6 ]. 6 Approximate doubling of the extinction coefficients on going from the free ligands (Fig. 1) to the complexes is consistent with the formation of the homoleptic species.The intense, high-energy bands are similar for all the complexes, and a small red-shi is observed for the MLCT band from 483 nm for the uoro-containing complex to 488 nm 6 for the bromo-derivative.The mixture of [Cu( 5 1, and a representative cyclic voltammogram (with internal Fc/Fc + reference) is shown in Fig. 7.Each complex exhibits a copper-centred oxidation process and the introduction of the F, Cl or Br substituents has only a small effect on its potential.In each of [Cu(2) 2 ][PF 6 ] and [Cu(3) 2 ][PF 6 ], the irreversible ligand-centred reduction process ca.À2.0 V is more pronounced in the rst cycle than in subsequent scans.

Comparison of the performances of the copper(I) dyes in DSCs
Surface-immobilized copper(I) dyes were assembled on commercial titania electrodes by initial adsorption of the phosphonic acid anchoring ligand 1 followed by treatment with CH 2 Cl 2 solutions of the labile [30][31][32] 2 and are compared to data for a DSC with standard dye N719.The right-hand column in Table 2 gives the   energy conversion efficiencies, h, relative to N719 arbitrarily set to 100%.We have recently adopted this presentation of results to provide a valid means of comparing data recorded using different solar simulators. 34For each DSC, the efficiencies were measured on the day of sealing the cell and then three and seven days later.
The rst point to note is that the DSC parameters for the dye [Cu(1)(4)] + (bromo-substituents) are comparable with those we have previously reported, 6 despite differences in electrode origins.In the present work, the photoanodes are commercially available titania electrodes which include a scattering layer; in our previous study, screen-printed electrodes with scattering layer were prepared in our laboratory.A second important point is that the data in Table 2 for corresponding pairs of DSCs conrm reproducibility of measurements.
On the day of cell fabrication, all four dyes (Table 2) perform relatively well with the global efficiencies, h, dependent upon the halo-substituent in the order I > F z Br > Cl.Upon aging of the DSCs, there is a general trend for improvement of    performance (Table 2).Over a three day period, the DSCs containing the iodo-substituted dye [Cu(1)( 5)] + show a ripening effect with h increasing from 2.88 to 3.01%, and 2.89 to 3.04% for the two independent DSCs.Aer a further four days, the efficiencies increase to 3.16 and 3.07%, respectively.][37] In terms of h, the best performing DSCs aer 7 days are those with iodo-dye [Cu(1)(5)] + which show power conversion efficiencies of 40.2 or 41.4% with respect to N719 set at 100%.For the aged DSCs, the dependence of h on the halo-substituent follows the trend I > Cl z F z Br.Fig. 8 shows J-V curves for DSCs containing anchored dyes [Cu(1)(2)] + , [Cu(1)(3)] + and [Cu(1)(5)] + ; data for the bromo-containing dye [Cu(1)(4)] + essentially replicate those already published. 6All J-V curves show good ll factors.The most signicant features in Fig. 8 are the enhancements in both short-circuit current density and open-circuit voltage over time for the chloro-and iodo-containing dyes (Fig. 8b and c).For [Cu(1)(5)] + (iodo), a maximum value of V OC ¼ 604 mV is achieved aer 3 days with no further improvement over the next 4 days (Fig. 8c); 604 mV compares with V OC (max) ¼ 664 mV for N719 measured under the same conditions are the copper(I) dyes (Table 2).Enhancement in the open-circuit voltage with aging of the DSC has also been noted for other copper(I) dyes. 38he EQE spectra of the DSCs were measured over a period of a week following cell fabrication.All show EQE maxima corresponding to l max in the range 460-480 nm (Table 3).The values of EQE max for the copper(I) dyes compare to EQE max z 75% for N719 (Fig. 9).Within experimental error, the EQE values for the cells containing [Cu(1)(2)] + and [Cu(1)(4)] + do not change with time, remaining around 46-47%.For DSCs with [Cu(1)(3)] + (chloro) or [Cu(1)(5)] + (iodo), a small enhancement in the EQE is observed up to 50 or 51%, respectively aer 3 days with no further improvement (Fig. 9).Fig. 10 2 and Fig. 8).The differences in the EQE spectra in Fig. 10 also correspond to the dependence of h on the halo-substituent (I > Cl z F z Br) for the aged cells described earlier in this section.

In situ dye assembly
Because the assembly of the best-performing dye [Cu(1)(5)] + was carried out using a mixture of [Cu(5) 2 ] + and [Cu(5)(MeCN) 2 ] + in the dipping process, we decided to assess a new strategy which eliminates the need to prepare the homoleptic copper(I) complex.The electrode functionalized with anchoring ligand 1 was immersed in a CH 2 Cl 2 solution containing a 1 : 1 mixture of [Cu(MeCN) 4 ][PF 6 ] and 5 (Scheme 4); the concentration of each was 0.1 mM.Over the dipping period of 68 hours, the electrode became pale red-orange and the colour persisted aer drying.Duplicate cells were prepared and  View Article Online the DSC characteristics compared to an N719 standard are given in Table 4.
The performances of the duplicate DSCs are similar and exhibit efficiencies of 2.80 or 2.71% aer 7 days.One cell shows an enhanced performance over the 7 days aer sealing the DSCs (Table 4) and both cells exhibit improved V OC but little change in J SC (Fig. 11).The EQE spectra for the two DSCs show maxima at 46.0 and 46.1% (l max ¼ 470 nm) on the day of cell fabrication and these values vary little over a 7 day period (Fig. 12).Overall, the performances of the DSCs containing dye [Cu(1)(5)] + assembled in situ are comparable with those of the DSCs made by ligands exchange.The differences in performance (compare the entries for [Cu(1)(5)] + in Tables 2  and 4) are not signicant and imply that isolation of the homoleptic copper(I) complex is not an essential part of the cell-assembly process.

HOMO and LUMO characteristics
We have used ground state DFT calculations to gain some insight into the origin of the surprisingly good performance of dyes containing iodo-substituted ligand 5. We have previously shown that the choice of atomic orbital basis set (6-311++G** basis set on all atoms, 6-311++G** on copper and 6-31G* basis set on C, H and N, or 6-31G* basis set on all atoms) has a strong inuence on the calculated absorption spectra of representative bis(diimine) copper(I) dyes, while the orbital characteristics of HOMOs and LUMOs are essentially    showed that the energies and characteristics of the LUMO and LUMO+1 of the four complexes are similar.The LUMO is centred on the anchoring ligand while the LUMO+1 is principally localized on the bpy domain of the ancillary ligand.These MOS are shown for the iodo-complex in Fig. 13a and b.The close similarity in the orbital characteristics for the four dyes suggests that the enhanced performance of [Cu(1)(5)] + is not associated with a tuning of the properties of the lowest lying vacant MOs leading to improved electron injection.
The DFT calculations indicate that the HOMO of each ground-state dye is mainly based on copper, as are the next two highest occupied MOs.Ancillary ligand character is present in HOMOÀ3 and HOMOÀ4 in [Cu(1)(5)] + , with a dominant contribution from the iodophenyl substituent (Fig. 13c).Signicantly, the corresponding contributions by ligands 2, 3 or 4 to these MOs is smaller.This leads us to suggest that the better dye performance of [Cu(1)(5)] + may be associated with improved hole transfer over the halogen of the aryl substituent to the reduced electrolyte.
The observation that DSCs containing [Cu(1)(5)] + give global efficiencies >3% is unexpected and has signicant potential in terms of the use of a synthetically very accessible ancillary ligand.The same level of efficiency can be achieved with [Cu(1)(5)] + assembled using a 1 : 1 mixture of [Cu(MeCN) 4 ] + and 5 in place of [Cu(5) 2 ] + .This not only avoids the need to prepare the homoleptic complex, but also prevents the wastage of one equivalent of ancillary ligand.Our next challenge is the optimization of the DSCs with [Cu(1)(5)] + and related dyes, starting with an investigation of the role of coadsorbents such as cheno.

Scheme 1
Scheme 1 Structures of ligands with atom labelling for NMR spectroscopic assignments.
3 and 589.2, respectively, corresponding to [M + H] + .The 1 H and 13 C NMR spectra were assigned by COSY, HMQC and HMBC methods and are consistent with the disubstitution pattern shown in Scheme 2. Broadening of the signals for H A3 and H A5 (see Scheme 1 for atom labelling) is most likely associated with rotation of the 4-halophenyl groups on the NMR timescale.At 500 MHz, values of FWHM for the signals for H A3 and H A5 are 36 and 12 Hz, respectively in 2, and 21 and 17 Hz in 5.The solution absorption spectra of compounds 2-5 are compared in Fig. 1, the intense high energy bands arising from p* ) p and p* ) n transitions.The highest energy absorption shis from 248 nm in 2 to 260 nm in 5.

The 1 H
and 13 C NMR spectra of a CD 3 CN solution of [Cu(2) 2 ][PF 6 ] were consistent with a single ligand environment, and the aromatic region of the 1 H NMR spectrum is shown in Fig. 2a.Coupling to 19 F gives characteristic signals for protons H B2 and H B3 and doublets for all ring B resonances in the 13 C NMR spectrum (see Scheme 1 for numbering), and the assignments were conrmed through the HMBC and HMQC spectra.The methyl groups give rise to sharp singlets at d 2.35 and 25.2 ppm in the 1 H and 13 C{ 1 H} NMR spectra, respectively, of [Cu(2) 2 ][PF 6 ], and these shis are unchanged on going to [Cu(3) 2 ][PF 6 ].The aromatic region of the 1 H NMR spectrum of a CD 3 CN solution of [Cu(3) 2 ][PF 6 ] is shown in Fig. 2b.The change from uoro to chloro substituent has the greatest effect on H B3 in keeping with expectations. 29Preparation of the iodo-containing complex [Cu(5) 2 ][PF 6 ] proved more problematical.The method used was as for the uoro-, chloro-and bromo-containing complexes, but repeated purication of the bulk sample failed to produce analytically pure [Cu(5) 2 ][PF 6 ].In contrast to the sharp singlet for the methyl protons in [Cu(2) 2 ][PF 6 ] and [Cu(3) 2 ][PF 6 ], the room temperature 1 H NMR spectrum of the iodo-containing product showed a very broad signal centred at d 2.52 ppm with FWHM $145 Hz.The 13 C NMR resonance for C Me could not be resolved at 295 K and no cross peak for the H Me signal was observed in the HMQC spectrum.The signals for H A3 and H A5 were also broad (Fig. 2c).Cooling the sample to 240 K led to collapse of the broad peaks and appearance of two sets of signals (Fig. 3), consistent with two environments for coordinated ligand 5 (the free ligand is poorly soluble in acetonitrile and therefore signals arising from ligand can be discounted).The separations of pairs of signals for H Me indicate that the two methyl groups are signicantly different in the two species (d 2.26 and 2.83 ppm), and similarly for the two H A3 protons (d 8.42 and 8.66 ppm).The local environment of H A5 appears similar in the two species, and similarly for H B2 and H B3 .We propose that the bulk material contains a mixture of [Cu(5) 2 ][PF 6 ] and [Cu(5)(MeCN) 2 ][PF 6 ], and that at 295 K, ligand exchange occurs between [Cu(5)(MeCN) 2 ] + and [Cu(5) 2 ] + .This is supported by the electrospray mass spectrum of the bulk material which exhibited peak envelopes with a characteristic copper isotope pattern at m/z 1239.3 and 692.2 arising from [Cu(5) 2 ] + and [Cu(5)(MeCN)] + ; the base peak (m/z 589.2) was assigned to [5 + H] + .The identity of [Cu(5)(MeCN) 2 ][PF 6 ] as one component of the mixture was conrmed by a single crystal structure determination of orange blocks that grew during recrystallization of the bulk material (see Experimental section).Fig. 4 shows the structure of the [Cu(5)(MeCN) 2 ] + cation in [Cu(5)(MeCN) 2 ][PF 6 ].

Fig. 5
Fig. 5 (a) Face-to-face p-stacking of phenylbpy domains (spacefilling representation) involving the phenyl ring with C12 leading to infinite assemblies following the c-axis.View down the c-axis showing the two different [PF 6 ] À environments.Anion with P1 is shown in green, and with P2, in red; CH/F contacts are shown by red hashed lines.

Fig. 9
Fig. 9 EQE spectra for duplicate DSCs functionalized with [Cu(1)(5)] + measured on the day of sealing the cell (day 0) and 3 and 7 days later, compared to the EQE spectrum of a DSC with N719.

Fig. 11 J
Fig. 11 J-V curves measured over a 7 day period for one of the DSCs containing [Cu(1)(5)] + formed in situ by stepwise assembly.

Fig. 12
Fig. 12 EQE spectra measured over a 7 day period for one of the DSCs containing [Cu(1)(5)] + formed in situ by stepwise assembly.

Table 2
Performance data for two independent sets of sealed and masked DSCs with copper(I) anchored dyes; data are with respect to standard dye N719 measured under the same conditions.J SC ¼ shortcircuit current density; V OC ¼ open-circuit voltage; ff ¼ fill factor

Table 3
EQE maxima for two independent sets of DSCs containing dyes [Cu(1)(L)] + L ¼ 2, 3, 4 or 5 measured on the day of cell fabrication and 3 days later This Open Access Article.Published on 06 October 2014.Downloaded on 9/15/2023 11:35:49 PM.This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.

Table 4
Performance data for two independent sets of sealed and masked DSCs with dye [Cu(1)(5)] + assembled in a stepwise manner; data are with respect to standard dye N719 measured under the same conditions